153. The variety of ground signals used in Naval pyrotechnics produce signal stars (pa-rachute borne), clusters of five stars which fall free, and other special effects. Each single consists of a cylindrical signal case six inches long and 1.6 inches in diameter, equipped with a tail and fins to stabilize it in flight. They are fired from a ground signal projector of a rifle grenade launcher, and the proper firing mechanism must be used with each signal. The signal is protected to about 600 feet altitude, where the expelling char-ge ignites and ejects the signal contained in the cylindrical case. A time fuze, with a de-lay of six seconds, is provided so that the case may attain the altitude as the expelling charge ignites. Signals are of two types, one for use with Ground Signal Projector M3 and M4, and one for use with service rifle of carbines equipped with the proper grenade laun-chers. The firing mechanism for each type will be found following the description of the type.